1. Field of the Invention
This invention relates to a cardiac pacer for pacing a heart, in particular a human heart, wherein the pacing rate is controlled by body activity, for example respiration.
2. Related Applications:
The subject matter of the present application is related to the subject matter of the following co-pending applications filed simultaneously herewith: "A Cardiac Pacer For Pacing A Human Heart," Amundson, Ser. No. 874,588; "A Cardiac Pacer For Pacing A Heart," Elmqvist, Lekholm, Hedberg and Amundson, Ser. No. 874,597; "A Cardiac Pacer For Pacing A Heart," Lekholm and Amundson, Ser. No. 874,596; and "A Cardiac Pacer For Pacing A Human Heart," Lekholm and Amundson, Ser. No. 874,591.
The European Patent Application No. 0,089,014 describes a cardiac pacer where the signal received from an impedance measurement is compared with two threshold levels. Signal portions which lie outside the width of the two threshold levels are discarded from further signal processing since they are considered as impedance variations which do not have a certain consistency and therefore cannot contribute to possible evolution of a respiratory act. Only those portions which lie inside the width of the two threshold levels are further utilized for evaluation.